Help!Everything BUT brake lights work with new wiring...Help

[kayakrguy]

Hi folks,

We got a new Hyundai Sonata to take West this summer. Wife uneasy with the 160K Altima, and to put her mind at ease we got the Sonata.

Here's the problem: I had the Sonata wired for towing. Tried it out in garage here at house. Everything works BUT the brakes...what would be the reason for that? Emergency flashers, running lights and turn signals all work, but brakes don't light when the pedal is pushed.....

Thanks,

Jim

[Miriam C.]

When mine did that it needed extra grounding. Seems the brake lights take more power. I just added an extra ground to the lights themselves.

[kayakrguy]

Hi Miriam,

Wow--if that works that would be neat!

Just how did you 'add' ground to your outfit? I'm assuming it makes a difference where/how you add it?

Thank you very much for the help!

Jim

[asianflava]

Try hooking it up to a different vehicle to verify that it isn't the trailer harness in the car.

Mine was acting funny like that. Everything worked except for the passenger side brake light. That was really strange because the turn signal and tail lights worked which means that both filaments in the bulb are OK. It also meant that the wiring was OK.

I finally hooked it up to my old truck and everything worked. The difference between the truck and my my wife's SUV is that the SUV uses a logic box for the trailer harness and the truck has a T-tap for the lights. I got a different trailer harness for the SUV and everything works fine.

[kayakrguy]

Rocky,

Thanks for the info....I have no idea what a T tap and a Logi box are or how I would know the difference....

In our case, we are a one-car family, so I can't do the 2 vehicle test you recommend. My brother in law tows a boat with a subaru, but he lives some 200+ miles away, so can't do that

The trailer worked fine with the Altima. So using your example, is there any way to check whether the Altima and the Hyundai us T-taps-Logic Boxes or..????--as in are there any tech specs I can refer to somewhere about that?

Thank you again

[brian_bp]

Does the trailer have separate (from the brake lights) turn signals? Or does it combine them like a traditional North American car or trailer? Both the Altima and the Sonata likely have separate turn signals.

If the trailer has combinged lights, and the cars have separate lights, then there needs to be some sort of converter (the "logic box") in between them, normally installed as part of the wiring in the car.

A "T-tap" is just a connector: you unplug the car's tail lamp assembly from the the car's wiring, plug both of those connectors to the T-connector, and the third side of the tee is the set of wires carrying the "tapped" signals. It saves splicing into the car's wires.

If everything is working except the brake lights, and the Sonata has separate turn signals, and the trailer uses a combined system...
perhaps the Sonata is missing the required converter, or the converter is faulty, or just the one wire tapped into the brake circuit has a bad connection.

I would start from the connector on the back of the car:
- if it only has four pins, the trailer is a combined system
- if it has more, maybe it's a separate system
- I would check for power at that connector - without the trailer attached - to see if the right wires have power at the right time

[kayakrguy]

Hi Folks,

First, thanks to everyone for their replies. Really focused and motivated me.

Good News...after Miriam's suggestion about grounding the lights, I decided to do that FIRST The reason being that MJ and others had suggested the same thing a long time ago, but I never got around to it.
So, I connected both lamps directly to the ground coming from the car.

Bad News...with the new grounds, all the problems got WORSE
For one thing, the left trailer tail light quit working, period. The left turn signal no longer worked on either the car or the trailer...BUT...the left turn signal indicator on the dash turned on and stayed on, even after I turned off the turn signal. The emergency flashers no longer wlorked on the trailer and the only running lights and turn signal that worked were the right ones. Brake lights STILL did not work.

I knew I had a problem.

So, using the trusty tutorial for testing the wiring on the Tow vehicle, I got my test light out and went through the drill. With the left turn signal on, nada. With the right turn signal on, nada. Basically the only thing that was ok was the ground. At that point I figured the connector was the problem. I called the folks who did the job and took it in....

Good News--it WAS the connector....they put a wrong one in...guy grabbed a box, gave it to the mechanic, so the mechanic put it in....problem was boxes are too similar, even tho they have different connector.

So things are fixed, got lights etc. The only thing I cannot figure out is: didn't the mechanic test his work before giving me the car the first time??? Ordinarily this place does A-1 work--in a substantial area of the Jersey shore, they are the hitch and wire place to go to--trucks especially.

Anyhow, thank you all very much!!

Jim